Our project concerns the entry of mast cells into the CNS. Mast cells are best known for their role in inflammatory disease. However, they also exist in the CNS and are pluripotent as to the possible secretory products they can release. We have discovered that their numbers in specific brain regions appear to be controlled by developmental age and reproductive status. The goals now are to analyze at a cellular level how they enter the CNS (both physical pathways and potential chemotactic agents) and how they influence the brain vasculature and neuronal transmission. We have also begun looking for a functional role of mast cells in the brain. These could include regulating core body temperature after induction of sepsis and also influencing behavior. The implication of mast cells in arousal and behavior like fear and anxiety would be novel evidence for an immune cell's contribution to the neural basis of behavior.